Combined fuse holder and indicating lamp unit



y 5, 1964 A. F. BULGIN 3,132,224

COMBINED FUSE. HOLDER AND INDICATING LAMP UNIT Filed April 11, 1962 Attorney United States Patent 3,132,224 COMBINED FUSE HOLDER AND INDICATING LAMP UNIT Arthur Frederick Bulgin, Barking, England, assignor to A. F. Bulgin & Co. Ltd., Essex, England, a British company Filed Apr. 11, 1962, Ser. No. 186,676 3 Claims. (Cl. 200121) This invention relates to cartridge fuse holders of the type which comprises asubstantially tubular body which can be fixed to a mounting panel so that .the front end of the body, which is open, is in front of the panel. The fuse is housed within the body and the open end is closed by means carrying a grip for fitting over one end of the fuse. Holders of this sort allow quick replacement of a fuse from the front of the panel.

According to the invention the means comprises a member carrying both the grip .and a lampfor indicating when the fuse breaks down, a sleeve surrounding the member along part of its length and formed with screw threads engaging matching threads on the body at its, open end, and a coiled compression spring housed between the sleeve and the member and bearing at one end on an internal shoulder of the sleeve and at the other end on a flange on the member to bias it into the body.

The provision of this spring means that the sleeve and member may rotate independehtly to some degree, so

' that when the -fuse is in its proper position within the body the sleeve may continue to rotate until it is screwed fully home. When in this position the spring forces the grip against the fuse capjthus ensuring a good electrical connection." The independentrotationbetween the sleeve and the member also allows themember to be rotated after the sleeve is screwed fully home to allow, for example, a translucent cap fixed to the member and covering the lamp to bealigned so that any word such as Fuse engraved on the cap may appear horizontally.

Alternatively the translucent cap may be rotatably fixed to the member so that this alignment may be carried out withoutproducing relative rotation between the member and the fuse.

A fuse holder according to the invention will now be described in more detail by way of example with reference to the accompan'ylng drawings in which:

FIGURE 1 is an exploded view showing parts of the holder in elevation; and

FIGURE 2 is a longitudinal cross section through the assembled fuse holder.

The holder comprises a substantially tubular body 1 V which ends in an enlarged flange 2 surrounding an open endof the body. The part of the body below the flange 2 is formed with external threads 3 and a nut 4 is provided to cooperate with these threads so that when the holder is fitted to a mounting panel the panel is held between the flange and the nut so that the open front of the body is on the front side of the panel while the remainder of the body is hidden from view. Housed within} the closed end ofthe body is a stud 5 having a shank 6 projecting through a conducting sleeve 7 in the end of the body and ending in a tab 8 to which may be soldered an electrical connection to the live role of a supply. A compression spring 9 acts between the bottom of the body and the lower surface of the stud and biases the stud towards the open end of the body.

A cartridge fuse 10 can be housed within the body and when it is in position one of its caps 11 is in contact with the stud 5. The other of its caps 12 is held in a grip 13 fixed on the end of a member shown generally at 14. At the end opposite the grip 13 the member 14 carries a neon lamp 15 which is electrically connected by a con ducting rod 16 passing through the cent-re of the member to the grip -13. The part of the body 17' surrounding this rod is made of insulating material. The member is surrounded along part of its length by a sleeve 18 which is externally threaded as at 19 the threads being arranged to mate with internal threads 20 in the open end of the body. The member 14 is a sliding fit within the sleeve and a compression spring 21 is housed between the sleeve and the member and bears at one end on an internal shoulder 22 of the sleeve and at the other end on a flange 23 of the member.

The sleeve 18 is formed with a knurled ring 24 of diameter greater than the diameter of the threaded section 19 and by means of this the sleeve can be screwed into and out of the body. When the sleeve is being screwed home it carries the member so that the two rotate together but when the fuse is in its proper position within the body it is not desirable to continue rotation of the member even though the sleeve may not be screwed fully home; Since therefore the two are a sliding fit together it will be seen that the sleeve can be rotated independently of the member so that when the resistance to rotation of the member reaches a certain level the sleeve only is rotated until it reaches the position shown in FIGURE 2.

A translucent cap 25 is provided for covering the lamp l5 and it will be seen that the cap has an enlarged flange 26 which fits within a recess 27 formed in the end of the sleeve and is held in the recess by an; inturned rim 28 of the sleeve. Although the cap is thus held so it cannot easily be removed, it is not prevented from rotation relafive to either-the sleeve or the member and if as is preferred the cap is engraved with a word such as Fuse it will be seen that once the fuse has been inserted into the holderand the sleeve screwed fully home the cap may be rotated so that the word may be aligned as required.

As previously mentioned one of the electrical contacts for the fuse is made by way of the tab 8. The other is by way of the grip '13 and it will be seen that the lower edge of this grip bears on a metallic ring 29 located against a shoulder 30 within the body. Two tabs 31 project from this ring through the wall of the body and the wall is recessed as indicated at 32 so that the tabs do not project beyond the remainder of the outer surface of the body. The connection of the grip 13 to the load can thus be made by way of either of these tabs. It will be remembered that one of the connections for the neon lamp is also taken from the grip 13 so that the tabs 31 also form one point of connection for the leads to this. If the lamp is required to light up when the fuse ruptures it must be connected in parallel with the fuse so that the other connection to the lamp must be by way of the tab 8. Accordingly a wire 33 arranged outside the body is soldered at one end to an extension of the conducting sleeve 7, and at its other end to a conductor 34 projecting through the wall of the body and extending upwardly within the body to a metal ring 35 held against a further shoulder 36 formed within the body above the shoulder 30.

One of the direct connections to the lamp is, as has been stated, the rod 16, and the other one is a metal cap 37 which surrounds the base of the lamp. The cup is formed integrally with the flange 23 against which the spring bears and there is also a further integral extension 38 which is fixed to the insulated part 17 of the member. One end of a compression spring 39 surrounding the insulating part 17 is fixed in good electrical contact with the extension 38 and the other end of this spring bears against a conducting washer '40 which is seated on the metal ring 35. An insulating disc 42 is mounted between m 3 V I the washer '40 and the grip '13. The path for current flowing through the lamp is thus from the'tab 8 through sleeve 7, wire 33, conductor 34, ring 35, washer 40, and

spring 39 to the cup 37, and from the rod 16 through the grip 13 and ring 29 to the tabs 31. Since the supply for the, fuse is also by way of the tab 8 and the tabs 31 it will be seen that the lamp is connected in parallel with the -fuse as required. I

A resistance 41 is connected with the wire 33 in the circuit to the lamp so that the resistance of the lamp circuit is greater than that of the fuse circuit and current flowsprincipally through the fuse so that the lamp is not lit. If the. fuse is overloaded and ruptures however the currentwill then flow through the lampicircuit and the lamp will light up thus giving an indication thatthe fuse.

has ruptured.

The provision of the various springs means that good electrical :contact is made Where required. Thus the spring 21, as well as ensuring contact between the fuse cap 12 and gripj13, forces the lower part of the grip against the ring 29, and the spring 39 forces the Washer 40 against the ring 35. The spring 9 works in opposition against the spring 21 and thus ensures that excellent electrical contact is made at each 'end' of the fuse. This spring also enables fuses differing slightly in length to be housedrirr the holder. I

It will be appreciated that certain modifications can be f made such as the provision of a filamentary instead of a neon lamp, and the adaptation of the, contacts so that the connections can be made in such away that the lamp will be extinguished, not lit, when the fuse ruptures.

I claim:

11a A cartridge fuse unit incorporating an indicator lamp for indicating break down of the fuse, said unit comprising: 7 a c I a substantially tubular body having a screw-threaded open outer end and a closed inner end;

a contact for the fuse at said inner end of said body;

a member having an outer end and an inner end;

a flange on said member intermediate its ends;

. a a an indicator lamp carried by said member at said outer end; Y

v a grip for said'fuse carried by said member at said 7 inner end;

the fuse being housed Within said body between said grip and said contact; I asleeve surrounding said member along part of its length, said sleeve being fixed to said body byscrew threads formed on said sleeve matching said screw' threads on said outer end of said body;

a shoulder formed on'said sleeve;

and a coiled compression spring housed between said sleeve and said member and bearing at one end on said shoulder of said sleeve and at the other end on 7 said flange on said member to bias said member into said body. a I I a 2. A cartridge fuse unit as claimed in claim 1 and including a translucent cap covering said indicator lamp.

3; A cartridge fuse unit as claimed in claim 1 and fur- I UNITED STATES PATENTS V Hornsby et al. Mar. 17, 1908 Anderson s Jan. 6, 1953 Linton Sept. 9, 1958 

1. A CARTRIDGE FUSE UNIT INCORPORATING AN INDICATOR LAMP FOR INDICATING BREAK DOWN OF THE FUSE, SAID UNIT COMPRISING: A SUBSTANTIALLY TUBULAR BODY HAVING A SCREW-THREADED OPEN OUTER END AND A CLOSED INNER END; A CONTACT FOR THE FUSE AT SAID INNER END OF SAID BODY; A MEMBER HAVING AN OUTER END AND AN INNER END; A FLANGE ON SAID MEMBER INTERMEDIATE ITS ENDS; AN INDICATOR LAMP CARRIED BY SAID MEMBER AT SAID OUTER END; A GRIP FOR SAID FUSE CARRIED BY SAID MEMBER AT SAID INNER END; 